The measurement of free (unbound) drug concentrations in plasma is important for certain drugs and has two advantages over measurement of total concentration: (1) the free concentration is independent of changes in plasma binding (e.g., due to changes in albumin), and (2) the free concentration is more directly related to both the efficacy and toxicity of the drug [PMID: 6636249] . For most drugs and the majority of patients, measuring the free and total concentrations is not necessary. However, for certain drugs, including some anticonvulsants and antibiotics, and specific patient populations, such as critically ill or immunosuppressed patients, the free concentration is a better indicator of therapeutic effect and potential toxicity.

Source: Regenstrief LOINC

BASIC ATTRIBUTES

Class/Type:

DRUG/TOX/Lab

Common Lab Results Rank:

#1581

First Released in Version:

1.0

Last Updated in Version:

2.52

Mass or Substance Property:

M

Order vs. Obs.:

Both

Status:

Active.Change Reason: Changed Order_Obs from 'Observation Only' to fit the current order use cases.

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